EP2388027A1 - Pump system with normal and special operation phase - Google Patents

Abstract

The pump system has a blood pump (5), which has a blood flow throughable housing (7) and a drive with supply elements. A control unit operates the blood pump alternating in a supplying operation and in a special operation. A drive parameter of the pump is changed during the special operation. An independent claim is also included for a method for operating a blood pump.

Description

The invention is in the field of mechanical engineering and micromechanics with applications in the medical sector, in particular in the design of small-sized pumps for use in cardiac support in mammalian bloodstream systems.

Diverse fluid pumps of a small design have become known which can be used temporarily or permanently for cardiac support in the event of insufficient function, especially of the human heart. Such pumps can be switched on invasively or non-invasively in the bloodstream.

An example is the introduction of such a pump via a blood vessel to one or in a heart chamber via a cardiac catheter, the respective pump typically having a compressed state for transportation and a potentially expanded state for post-shipment operation.

Another example is an implantable blood pump that is connected to blood vessels and heart via cannulas and can permanently effect support for the heart, such as the left ventricle.

Often, such pumps are rotor pumps having a drivable rotor with delivery elements for axial or centrifugal delivery of the blood. Wear-free, such a rotor, for example, be magnetically stored to achieve long service life.

Just as in the normal bloodstream of humans sometimes unwanted coagulations of the blood take place, which can develop up to thrombosis, this can not be ruled out even with a pump.

The invention is therefore based on the goal of avoiding and / or reducing such coagulation effects of the blood in the environment of a pump.

This object is achieved with the features of the invention according to claim 1.

The invention provides for a pump system, a blood pump, which has a flow-through by blood housing and a drive with a conveying element and a control device for controlling the blood pump, wherein the control device operates the pump alternately in the conveying operation and in a special operation, wherein in the special operation at least one drive parameter of the pump is changed so that at least one point along the flow path through the pump, the total volume flow is at least temporarily reversed.

Usually, such a blood pump is constructed with a rotary drive, for example as an axial pump with an impeller / propeller or as a centrifugal pump. But there are also other pump forms, for example, for pulsatile operation or generally with mechanical drive elements, in the form of volume variable displacement elements for conveying a fluid conceivable. In addition, all other principles, including diaphragm pumps or pumps with a drive by the action of electric or magnetic fields for the application of the invention are conceivable.

For the invention, it proves to be advantageous that from time to time a special operating phase between delivery operating phases is inserted, wherein the special operating phase provides a change in at least one drive parameter at least to the extent that at least at one point along the flow path through the pump, the total volume flow at least temporarily is reversed.

In the case of pumps with rotating elements, the drive / rotational speed may be considered as changeable drive parameters.

The invention is, for example, on pumps with rotationally drivable conveying elements such as propellers applicable so that the speed is changed or the angle of attack of a conveying element / propeller is changed. It can also be the degree of expansion, such as flip angle of conveyor elements are changed, if this is specifically possible. In pumps that use to promote the fluid of a variable volume element, the amplitude of the volume change or the frequency of the volume change can be changed accordingly. Decisive for the effect of the invention is in particular that change at many points of the flow, especially where coagulation can take place, the flow conditions, at least temporarily or even reverse. In this context, so-called dead water areas are known in which very low flow velocities prevail and thus coagulations can be favored. In addition, such coagulations may also be generally favored at flow obstacles. The invention can advantageously bring about changes in the flow conditions by changing the drive parameters, especially in such areas. Usually, the total volume flow through the pump will temporarily reverse. Nevertheless, assuming incompressible delivered liquid, the total volume flow may be different at different locations along the flow path when short term housing volume changes are considered. In particular, in pump housings with flexible membranes such housing volume changes may occur with changes in the flow conditions, even if they are of minor importance in normal operation.

In the aorta, this is achieved by the physiologically effective so-called Windkessel function, which in normal physiological process during the maximum pressure phase of the systole caused by a yielding of the vessel walls, a storage of a partial blood volume, which is nachgieben with decrease in pressure by the contraction of the vessel walls. As a result, the blood flow is made uniform. In the present case of a special operation, the effect can lead to a repulsion of the blood against the main flow direction.

In addition, a purging of the ventricle can be achieved by a special operation phase, and there may be an occasional opening of the aortic valve.

An advantageous embodiment of the invention provides that the blood pump has an inlet opening and an outlet opening, wherein a reduction of the delivery rate of the pump during the special operation is dimensioned such that averaged over at least one point between the inlet opening and the outlet opening of the area average value of the axial velocity Flow cross section at least once temporarily changes its sign.

Here, the axial velocity profile is understood as meaning the profile of the axial velocities of infinitesimal volume elements over a cross section of the flow path. The integral over this flow cross-section with respect to the axial velocity distribution thus gives the total current. If the mean value of the axial velocity profile changes, this is accompanied by a change in the integral and thus the total current intensity of the liquid flow.

Already changes in the axial velocity profile can advantageously affect the prevention of coagulation according to the invention, since this means the displacement of vortices within a flow cross-section. However, the at least temporary reversal of the total flow at a point along the flow path has turned out to be particularly advantageous.

It has proved to be particularly advantageous for the invention, when the total volume flow at an inlet opening and / or an outlet opening of the pump housing at least once reversed its direction temporarily. It may well also be provided that the total volume flow during a special operation several times a direction opposite to the conveying operation and temporarily takes a corresponding to the conveying operation direction. This produces successive changes in direction of the flow, whereby a non-stationary flow with chaotic migration of the turbulence is achieved, so that most likely all volumes within the pump housing can be acted upon by changing flow conditions.

It is particularly advantageous if, during a special operation at several points, in particular at all points of the flow path through the pump, the total volume flow is at least once reversed.

It has also proved to be advantageous if the time integral of the delivery flow over a whole special operating phase is negative.

This means that in fact the pump temporarily carries a certain volume from the outlet opening to the inlet opening, which is moved through the pump only after resumption of the conveying operation.

The invention further relates to a pump system with a blood pump, which has a housing through which blood can flow and a drive with a delivery element, and with a control device for controlling the blood pump. In addition, the invention provides that the conveying element of the pump is designed as a rotor and that in the control device at least a first speed level of the rotor for the conveying operation and at least one Sonderbetriebsdrehzahlniveau is provided for a special operation, said at least one Sonderbetriebsdrehzahlniveau provides a lower speed of the rotor as the conveyor operation.

Advantageously, in special operation, the special operating speed is lowered so far that the above-described reversal of the total volume flow is achieved at least temporarily and at least at certain points of the flow path.

It can also be provided that a constant special operating speed level, in particular the lowest special operating speed level, is provided over a period of time during a special operating phase.

In this case, the speed can be reduced at the beginning of the special operation via a linear ramp, then constant to a special operating speed level held and then controlled by another ramp again to the conveyor mode.

It is also a sawtooth waveform control of the speed possible, so that the minimum speed is achieved in special operation only for a moment.

The invention may also relate to a pump system with a blood pump having a blood-flowable housing and a drive with a conveying element and a control device for controlling the blood pump, wherein the conveying element of the pump is designed as a rotor, wherein it is provided that the Control device provides a first speed level of the rotor for the conveying operation and at least one special operating speed level for a special operation, and wherein the speed during a special operation at least temporarily at least 2000 U / min, in particular 2500 U / min, more particularly 3000 U / min or 4000 U / min below the speed in normal operation.

At usual speeds of blood pumps with rotors, which may be, for example, at 7500 rpm or even at 10,000 rpm, the reversal of the direction of flow of the blood in special operation is already achieved in many cases with the measures of the speed reduction.

The invention relates except to a pump system of the type described above also to a method for operating a blood pump, which is introduced into the bloodstream of a patient, wherein the pump is driven alternately in the conveying mode and in the special mode, the special operation at least temporarily causing a reversal of the total volume flow at at least one point along the flow path between an inlet port of the pump and the next cross-sectional constriction of the flow path behind the outlet port of the pump, in particular between the inlet port of the pump and the outlet port of the pump.

Corresponding special operating phases can advantageously be between 0.5 seconds and 1.5 seconds long and, for example, inserted at least twice per minute, once per minute or only every five to ten minutes between the conveying operating phases.

According to the operating method according to the invention can also be provided that during a special operating phase, the speed of the pump is lowered to a special operating speed and then raised again.

To achieve the desired effect on the flow, other parameters of the pump, such as an angle of attack of impeller / rotor blades, may also be changed. If at the same time the flow direction and / or the pressure is detected at suitable points of the flow path, a corresponding parameter can also be regulated. Usually, however, sufficient control, particularly easy control of the speed.

For this purpose, it may be provided according to the invention that the at least one special operating speed level is at least 25%, in particular 40%, more particularly 50% or 60%, or at least 2000 rpm or 3000 rpm below the rotational speed of the conveying operation lies. In this case, advantageously 0.1 to 2 special operating phases, in particular between 1 and 2 special operating phases, can be inserted per minute.

In the following the invention will be shown with reference to an embodiment in a drawing and described below.

It shows

Fig. 1

a schematic overview of a blood pump that is at least partially inserted into a heart chamber by means of a catheter,

Fig. 2

a schematic overview of a control device and a diagram that describes the operation of a pump,

Fig. 3

schematically the structure of a pump in three-dimensional view,

Fig. 4

schematically the construction of a rotary pump as a centrifugal pump in three-dimensional view,

Fig. 5

schematically shows the structure of a pump that works with a controllable displacement element,

Fig. 6

a pump in three-dimensional view that looks like a pump Fig. 5 works with a volume-variable expansion element,

Fig. 7

schematically the flow path in a pump housing,

Fig. 8

schematically the time course of the speed of a pump or a pump rotor,

Fig. 9

3 is a schematic view of a pump housing with a rotor and the corresponding fluid flow;

Fig. 10

another schematic view of the flow through a pump housing,

Fig. 11

in a diagram the time course of the speed of a pump,

Fig. 12

Another form of the pump speed in a diagram.

Fig. 1 schematically shows a blood vessel 1, which opens into a ventricle 2 of a heart chamber, wherein a catheter 4 is inserted through the blood vessel 1 via a lock 3.

The catheter 4 extends almost into the ventricle 2, wherein at the end of the catheter, a blood pump 5 is arranged, which protrudes partially into the ventricle.

The blood pump 5 is able to aspirate blood via a suction opening 6 and expel it via outflow openings within the blood vessel 1 and thus at least assist or at least partially replace the cardiac function.

The pump 5 has in its interior within a housing on a rotor 7 which is rotatably driven by means of a driven shaft 8 in a rotational speed range of for example 7000 to 10,000 U / min. The shaft 8 protrudes proximally out of the catheter 4 and is connected to a drive motor 9.

The drive motor 9 can be controlled or regulated by means of a control device 10. In this case, for example, certain speeds or time-dependent speed curves can be specified.

The control device 10 can optionally be connected to one or more pressure sensors 11, 12 which can be positioned, for example, in the blood vessel 1, the pump housing or the ventricle 2 in order to measure the current pressure there. This pressure measurement can be used as an input variable, for example, for a control within the control device 10. However, it is normally sufficient to simply control the pump speeds. A measurement of the velocity distribution of the blood stream can also be made via a Doppler spectroscopy device whose analysis results can also serve as input variables for a control.

Fig. 2 shows a schematic representation of the control device, which has a first memory 13 for storing a pump speed in the conveying mode and a second memory 14 for storing a pump speed during the special operation. In addition, the control device 10 has a third memory 15 for storing the conveyor operating time lying between two special operating phases and a fourth memory 16 for storing the duration of a special operating phase or the slope of the ramps in the change of the speed to the transition between the conveying operation and the special operation.

The control device also has a functional part 17, which outputs the respectively current target rotational speed to the motor 9 by means of a time control using the stored data.

Fig. 3 shows a typical pump structure of a pump 5 for applying the invention with a housing 7, wherein in the housing, a hub 18 is rotatably mounted, which is connected to a drive shaft 8.

The hub carries at least one conveying element 19 in the form of a propeller or a helical structure which generates an axial thrust upon rotation on a fluid, represented by flow arrows 20, 21. The sucked liquid is ejected via discharge openings behind the pump, which is indicated by the flow arrows 22, 23.

The pump 5 is attached to the end of a catheter 1 at this.

Diaphragms 24, 25 are indicated schematically, which serve to seal the pump during the passage / transition between the blood vessel 1 and the ventricle 2.

The Fig. 4 shows a further pump for the application of the invention, which also has a rotor as in Fig. 3 shown pump, but operates on the centrifugal principle. For this purpose, a rotor 26 with blade surfaces 27 is rotatable in the pump housing 7 ' stored. The rotor 26 can be driven at high speed by means of the drive shaft 8, so that fluid is sucked from the top end 29 of the pump via an end face 28 of the rotor 26 and centrifugally ejected over the circumference of the pump housing 7 ', as indicated by the arrows 30, 31 can. On the circumference of the pump, a channel may be arranged, which captures the outwardly pressed blood and an outlet opening.

Such a pump is usually arranged at the end of a catheter 1. Their speed can according to the method of the invention as well as the pump Fig. 3 to be controlled.

Fig. 5 shows a pump that does not require any rotational drive elements and only has a controllable with respect to its volume drive element 32 in the form of a fillable pad. The cushion 32 is shown in full expansion with solid lines, while the dashed line represents the cushion in the compressed state 32 '.

If the pad is compressed, liquid is sucked into the pump interior 34 via the inlet opening by corresponding folding of the one-way valve 33. The valve 33 is a one-way valve which prevents the outflow of liquid from the pump interior. In contrast, the outlet valve 35 is designed as a one-way valve only for the outlet of a liquid from the pump interior 34. Therefore, upon reexpansion of the pad 32, the inlet valve 33 locks and the displaced fluid can be discharged from the pump interior 34 through the outlet valve 35. Such a pump allows pulsatile operation with a periodically fluctuating flow.

In the Fig. 6 is a similar pump as in Fig. 5 shown, wherein the cushion 36 has in its center an opening 37 which is relatively small in the expanded state of the pad 36, shown as a solid line, but allows the passage of a liquid.

In the compressed state of the pad 36, the opening, as shown by the dashed line 38, greatly increased, so that in the pump interior 34 liquid is sucked. The function of the inlet and outlet valves at the ends of the pump interior 34 is identical to that shown in FIG Fig. 5 such that by periodically compressing and expanding the pad 36, a fluctuating flow is generated which is controllable with respect to its velocity amplitude and the frequency of the volume changes.

From the description of FIGS. 3, 4 . 5 and 6 It is clear that within the respective pumps, irrespective of the drive principle, different pump parts are flowed through or flowed through by the driven fluid flow, which in detail leads in some places to an increased or reduced flow velocity compared to the average as a result of vortex formation or similar effects. This may be the case, in particular, on a rotor or a drive pad, or else on support wheels that support the corresponding pump housings and on other support structures of pump housings whose outer skin can be constructed, for example, as a pliable diaphragm.

The Fig. 7 shows schematically and exemplarily a flow path through a pump housing 7, which is assumed idealistically cylindrical. In this case, two main flow arrows 39, 40 are shown, from which smaller vortices 41, 42 are released to all sides. This leads to a not completely homogeneous flow distribution within the pump cross-section. In this case, it is not necessary to actually generate backflowing vortices; it is also possible to generate an inhomogeneous axial velocity profile without backflow components at one point of the pump cross section.

Fig. 8 shows a diagram with a controlled over time according to the invention speed υ a blood pump or a pump rotor of such a pump on the vertical axis. The time axis is shown on the horizontal axis.

At time 0, the speed υ _{1 of} the normal conveying operation, typically 7500 U, is assumed, which is kept constant until time t ₁ . Between the time t ₁ and t ₂ , the speed drops linearly from υ ₁ to υ ₂ in the course of time, in order then to be kept constant between t ₂ and t ₃ at the speed υ ₂ . υ ₂ thus represents the minimum special operating speed.

Such a speed may, for example, be 3000 or 3500 rpm.

After the time t ₃ , the rotational speed is increased again to the delivery operating speed υ ₁ via a linear ramp between t ₃ and t ₄ . Thereafter, the conveying operation, for example, for half a minute or continue for one minute of constant speed before the next special operating phase is reached.

The Fig. 9 shows a pump housing 7 with a rotor 43 having propeller blades 44, wherein, for example, three pairs of propeller blades are provided in three different sections of a hub 45. The axial positions of these propeller blade pairs are indicated schematically on the right side of the illustration at 46, 47, 48.

In addition, a support wheel 49 with spokes on an axial position 50 and a support wheel 51 on an axial position 52 are shown schematically. The support wheels 49, 51 serve to support the housing membrane of the housing 7, which may be basically limp, and to keep corresponding axial inlet openings and outlet openings of the housing open.

The flow entering the pump housing 7 in the first support wheel 49 may form vortices at various locations along the flow path, as exemplified by the vortex 53 formed on the first support wheel 49 in the region of a spoke.

Vortexes can also arise on the propeller pairs, which are positioned in the axial heights 46, 47, 48 along the pump housing. Finally, vortices may also arise on the second support wheel 51, for example in the region of its spokes. Basically, of course, eddies can also occur in the area of the housing wall of the pump housing and the hub 45.

It is evident that by changing the flow velocity within the pump, the turbulences can be changed in their extent and can migrate in their spatial distribution.

Thus, it is possible by the invention to change flow conditions such that the coagulation of blood is prevented or slowed by temporary flow through otherwise weakly flowed areas.

For this purpose it may be sufficient to achieve a significant change in the flow distribution or a reversal of the total flow at one of the points along the flow path, that is, at the points 46, 47, 48, 50, 52; However, it may also be useful to effect this at several points along the flow at the same time or along the entire flow path. This state of flow reversal can be achieved in the short term, in order to then accept again the usual conveying direction in the conveying mode; During a special operating phase, such a change in the flow direction can also be provided several times.

However, it is also conceivable to maintain during a phase of the special operation for a while the reverse flow direction and thus to produce a net promotion of a fluid volume in the opposite direction of the usual conveying direction.

This is due to a reduced flow rate or speed of the pump and the external pressure conditions outside the pump, which counteract the flow direction during the normal delivery operation as a resistance / back pressure. The so-called Windkessel function of the aorta caused by the Elasticity of the vessel walls, which give in the region of highest pressure, a storage of a partial blood volume and when lowering the pressure, a back and forth pumping. The overpressure at the pump outlet can thus cause a backflow through a pressure difference to the pump inlet. These conditions are also dependent on the phase of the heartbeat when used in a heart, so that the initiation of a special operation phase can also be tailored to the heartbeat. In particular, the special operating phase can be controlled such that temporarily no blood is sucked out of the heart ventricle and this can be completely filled.

Also, a return flow from the blood vessel into the heart ventricle may be advantageous in order to achieve the effect according to the invention.

The heart ventricle can also be flushed through a special operating phase and an occasional opening of the aortic valve can be achieved.

The Fig. 10 schematically shows an ideal cylindrical assumed pump housing 7, in the centric along the cylinder axis, a strong flow, shown by the arrows 54, is initiated. It is shown that considerable turbulences 55 arise in the area of the housing wall. If the flow 54 is reduced / slowed by a reduction in the pumping stroke, for example, by reducing the rotational speed of a rotor or changing a pitch of rotor propellers, it is conceivable that the turbulences 55 are reduced or disappear in the course of generating a laminar flow. This would be a change of Flow conditions in the pump housing wall and thus cause a flushing of these areas.

The Fig. 11 shows by way of example two possible courses of rotational speeds of a rotor of a blood pump, applied vertically to time t on the horizontal axis.

The first course, denoted by 56, represents a sawtooth-shaped speed curve, within the scope of which, starting at a time t ₁ , the speed υ is linearly reduced from a delivery operating speed to a minimum special operating speed υ ₂ and immediately linear after reaching this special operating speed υ ₂ is increased to reach the Förderbetriebsdrehzahl.

In the area 57, a rounded profile of the speed is shown with a temporary reduction to υ ₂ .

The diagram Fig. 12 shows a further structure in which, starting at a time t ₁ , the rotational speed υ of the rotational speed of the delivery mode is lowered to a minimum special operating speed υ ₂ and then raised a bit far from this minimum special operating speed immediately. This happens several times during the special operation phase, so that the total flow direction of the blood flow can be reversed several times in this phase. This can be advantageous for the formation of a chaotic flow velocity distribution in the special operating phase in order to temporarily achieve a significant change in the flow velocity at each point of the flow cross section, before the conveying operation is resumed.

Overall, the pump system according to the invention and the operation of such a system according to the invention allows a change in the flow conditions, which, from time to time, in particular periodically, repeatedly, permanently prevents or at least slows down the formation of blood coagulation.

Claims (14)

Pump system with a blood pump (5), which has a blood flow-through housing (7) and a drive with a conveying element (19, 26, 27, 32, 36), and with a control device (10) for controlling the blood pump, characterized in that the control device operates the blood pump alternately in the conveying mode and in a special mode, wherein during the special mode at least one drive parameter of the pump is changed so far that at least one point (46, 47, 48, 50, 52) along the flow path through the Pump the total volume flow is at least temporarily reversed. The pump system of claim 1 including a blood pump having an inlet port and an outlet port, wherein a reduction in pump delivery during the special operation is sized such that at least one location (46, 47, 48) between the inlet port and the outlet port is the area average averaged over the flow cross section at least once its sign alternates the axial velocity profile. Pump system according to claim 1 or 2, characterized in that during the special operation at an inlet opening and / or an outlet opening the total volume flow at least once reverses its direction. Pump system according to claim 1, characterized in that during a special operation at several points (46, 47, 48, 50, 52), in particular at all points of the flow path through the pump, the total volume flow is at least once reversed. Pump system according to claim 1 or one of the following, characterized in that the time integral of the delivery flow over a whole special operating phase is negative. Pump system with a blood pump (5) having a blood flow-through housing (7) and a drive with a conveying element (19, 26, 27), and with a control device (10) for controlling the blood pump, wherein the conveying element of the pump as Rotor (19, 26, 27) is formed, characterized in that in the control device at least a first speed level of the rotor for the production operation and at least one Sonderbetriebsdrehzahlniveau (υ ₂ ) is provided for a special operation, wherein the at least one Sonderbetriebsdrehzahlniveau a lower speed of Rotor provides as the conveyor operation. Pump system according to claim 6, characterized in that the at least one special operating speed level by at least 25%, in particular 40%, more preferably 50% or 60%, below the speed of the conveying operation. Pump system according to claim 6 or 7, characterized in that over a period of time during a special operating phase a constant special operating speed level, in particular the lowest special operating speed level is provided. Pump system with a blood pump (5) having a blood flow-through housing (7) and a drive with a conveying element (19, 26, 27), and with a control device (10) for controlling the blood pump, wherein the conveying element of the pump as Rotor is formed, wherein the control device provides a first speed level of the rotor for the conveying operation and at least one Sonderbetriebsdrehzahlniveau (υ ₂ ) for a special operation, characterized in that the speed during a special operation at least temporarily at least 2000 U / min, in particular 2500 U / min , in particular 3000 U / min or 4000 U / min below the speed in normal operation is. Method for operating a blood pump (5) introduced into the bloodstream of a patient, characterized in that the pump is activated alternately in the conveying mode and in the special mode, the special mode at least temporarily reversing the total volume flow at at least one point (46, 47 , 48, 50, 52) along the flow path between an inlet port of the pump and the next cross-sectional constriction of the flow path behind the outlet port of the pump, in particular between the inlet port (50) of the pump and the outlet port (52) of the pump. A method according to claim 10, characterized in that a special operating phase between 0.5 seconds and 1.5 seconds. A method according to claim 10 or 11, characterized in that between 0.1 and 2 special operating phases per minute, in particular between 1 and 2 special operating phases per minute, are provided. A method according to claim 10, 11 or 12, characterized in that during a special operating phase, the speed of the pump is lowered to a special operating speed (υ ₂ ) and then raised again. A method according to claim 13, characterized in that the special operating speed is at least 25%, in particular at least 30%, more preferably at least 40%, 50% or 60%, in particular at least 2000 U / min or 3000 U / min, below the speed in the conveying mode ,

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